T-Nut for 4040 Extrusion M5 M4 M3 - rotates in

thingiverse

I use T-Nut with thread modelled for 4040 extrusion - print as designed, no additional nuts needed. You'll likely want to clean up the thread with a tap afterward. An alternative is clamping the nut in a vice and forcing a screw into the hole with an electric driver. Let it cool before removing the screw; the friction heat can create a nice thread but may cause expansion issues with critical dimensions. This method is worth trying if you're stuck. I tested the M5 version (PLA printed with 0.6mm nozzle), and adding significant torque without stripping the plastic thread was successful. Adding hex nuts is unnecessary for most purposes here. However, they have their own drawbacks in this design - the plastic around them can tear, rounding the hex slot hole, causing the nut to rotate when trying to undo the screw. This experience is not enjoyable. The design includes relatively tight tolerances; if you prefer a looser version, please leave a message.